Visible light communication method, identification signal, and receiver

ABSTRACT

A visible light communication method is provided that includes obtaining a first ID indicating a default interpolation ID previously stored in a receiver. The method also includes obtaining a second ID, by the receiver, through visible light communication with a light source, and generating a third ID, by the receiver, by combining the first ID and the second ID. The method further includes obtaining, by the receiver, information from a server using the third ID, which is a combination of the first ID and the second ID.

CROSS REFERENCE TO RELATED APPLICATIONS

The application is a continuation of U.S. application Ser. No.14/219,116 filed on Mar. 19, 2014, which claims the benefit of U.S.Provisional Patent Application No. 61/921,131 filed on Dec. 27, 2013.The entire disclosure of the above-identified application, including thespecification, drawings and claims are incorporated herein by referencein their entirety.

FIELD

The present disclosure relates to visible light communication methods.

BACKGROUND

In recent years, a home-electric-appliance cooperation function has beenintroduced for a home network, with which various home electricappliances are connected to a network by a home energy management system(HEMS) having a function of managing power usage for addressing anenvironmental issue, turning power on/off from outside a house, and thelike, in addition to cooperation of AV home electric appliances byinternet protocol (IP) connection using Ethernet (registered trademark)or wireless local area network (LAN). However, there are home electricappliances whose computational performance is insufficient to have acommunication function, or home electric appliances which do not have acommunication function due to a matter of cost, for example.

In order to solve such a problem, Patent Literature (PTL) 1 discloses atechnique of efficiently establishing communication between devicesamong limited optical spatial transmission devices which transmitinformation to free space using light, by performing communication usingplural single color light sources of illumination light.

CITATION LIST Patent Literature

[Patent Literature 1] Japanese Unexamined Patent Application PublicationNo. 2002-290335

SUMMARY Technical Problem

In such visible light communication, there is a demand for an increasedcommunication speed. Furthermore, the capability of providinginformation suitable for a user is desired in such visible lightcommunication.

Thus, a non-limiting and exemplary embodiment provides a visible lightcommunication method in which the increased speed can be achieved or theinformation suitable for a user can be provided.

Solution to Problem

A visible light communication method according to an aspect of thepresent disclosure includes: obtaining a first ID identifying an area inwhich a receiver is present; obtaining a second ID by the receiverthrough visible light communication in the identified area; andobtaining, by the receiver, information corresponding to a third IDwhich is a combination of the first ID and the second ID.

It is to be noted that these general and specific aspects may beimplemented using a system, a method, an integrated circuit, a computerprogram, or a computer-readable recording medium such as CD-ROM, or anycombination of systems, methods, integrated circuits, computer programs,and recording media.

Additional benefits and advantages of the disclosed embodiments will beapparent from the Specification and Drawings. These benefits and/oradvantages may be individually obtained by the various embodiments andfeatures of the Specification and Drawings, which need not all beprovided in order to obtain one or more of such benefits and/oradvantages.

Advantageous Effects

The present disclosure can provide a visible light communication methodin which an increased speed can be achieved or information suitable fora user can be provided.

BRIEF DESCRIPTION OF DRAWINGS

These and other objects, advantages and features of the disclosure willbecome apparent from the following description thereof taken inconjunction with the accompanying drawings that illustrate a specificembodiment of the present disclosure.

FIG. 1 is a block diagram of a visible light communication system inEmbodiment 1.

FIG. 2 is a flowchart of an area detection process performed by a mobileterminal in Embodiment 1.

FIG. 3 is a flowchart of a process performed by an area ID informationserver when area ID information is requested from the mobile terminal inEmbodiment 1.

FIG. 4 illustrates an example of an area ID information table held by anarea ID information holding unit in Embodiment 1.

FIG. 5 is a flowchart of a process performed by the mobile terminal whenthe mobile terminal receives the area ID information from the area IDinformation server in Embodiment 1.

FIG. 6 is a flowchart of a process performed by the mobile terminal whenthe mobile terminal receives a visible light ID from a visible lighttransmitter in Embodiment 1.

FIG. 7 is a flowchart of a process performed by the mobile terminal torequest ID correspondence information in Embodiment 1.

FIG. 8 is a flowchart of a process performed by an ID correspondenceinformation conversion server when the ID correspondence information isrequested by the mobile terminal in Embodiment 1.

FIG. 9 illustrates an example of a correspondence information table heldby an ID correspondence information holding unit in Embodiment 1.

FIG. 10 is a flowchart of a process performed by the mobile terminalwhen the mobile terminal receives a short ID from the visible lighttransmitter in Embodiment 1.

FIG. 11 is a flowchart of a process performed by the mobile terminal todisplay information in Embodiment 1.

FIG. 12 is a flowchart of a process performed by an interpolation IDgeneration unit to generate an interpolation ID based on a userattribute in Embodiment 1.

FIG. 13 illustrates an example of user information held by a userinformation holding unit in Embodiment 1.

FIG. 14 illustrates an example of a user attribute correspondence tableused by the interpolation ID generation unit to select the interpolationID based on the user attribute in Embodiment 1.

FIG. 15 is a flowchart of a process performed by the interpolation IDgeneration unit to identify an installation location of the visiblelight transmitter based on sensing data and reception camera informationin Embodiment 1.

FIG. 16 is a flowchart of a process performed by an interpolation IDgeneration unit to generate the interpolation ID based on theinstallation location of the visible light transmitter in Embodiment 1.

FIG. 17 illustrates an example in which the interpolation ID generationunit locates the visible light transmitter in Embodiment 1.

FIG. 18A illustrates an example in which the interpolation ID generationunit selects a front camera according to an orientation of the mobileterminal in Embodiment 1.

FIG. 18B illustrates an example in which the interpolation ID generationunit selects a back camera according to an orientation of the mobileterminal in Embodiment 1.

FIG. 19 illustrates an example of a location correspondence table usedby the interpolation ID generation unit to select the interpolation IDbased on a device location in Embodiment 1.

FIG. 20 illustrates a use case in Embodiment 1.

FIG. 21 illustrates a configuration example of an inquiry ID which istransmitted from the mobile terminal to the ID correspondenceinformation conversion server in Embodiment 1.

FIG. 22 illustrates an example in which the mobile terminal generatesthe inquiry ID in Embodiment 1.

FIG. 23 illustrates a detailed use case of Example 2 in FIG. 22 inEmbodiment 1.

FIG. 24 illustrates a detailed use case of Example 3 in FIG. 22 inEmbodiment 1.

FIG. 25 is a flowchart of a visible light communication process inEmbodiment 1.

FIG. 26 is a flowchart of the visible light communication process inEmbodiment 1.

FIG. 27 is a flowchart of the visible light communication process inEmbodiment 1.

FIG. 28 illustrates an example in which imaging elements in one line areexposed at the same time and exposure start time is shifted in the orderfrom the closest line in an imaging operation in Embodiment 2.

FIG. 29 illustrates a situation in which, after the exposure of oneexposure line ends, the exposure of the next exposure line starts inEmbodiment 2.

FIG. 30 illustrates a situation in which, after the exposure of oneexposure line ends, the exposure of the next exposure line starts inEmbodiment 2.

FIG. 31 illustrates a situation in which, before the exposure of oneexposure line ends, the exposure of the next exposure line starts inEmbodiment 2.

FIG. 32 illustrates the influence of a difference in exposure time inthe case where the exposure start time of each exposure line is the samein Embodiment 2.

FIG. 33 illustrates the influence of a difference in exposure start timeof each exposure line in the case where the exposure time is the same inEmbodiment 2.

FIG. 34 illustrates the advantage of using a short exposure time in thecase where each exposure line does not overlap another in exposure timein Embodiment 2.

FIG. 35 illustrates the relation between the minimum change time oflight source luminance, the exposure time, the time difference betweenthe exposure start times of the exposure lines, and the captured imagein Embodiment 2.

FIG. 36 illustrates the relation between the transition time of lightsource luminance and the time difference between the exposure starttimes of the exposure lines in Embodiment 2.

FIG. 37 illustrates the relation between high frequency noise of lightsource luminance and the exposure time in Embodiment 2.

FIG. 38 is a graph representing the relation between the exposure timeand the magnitude of high frequency noise of light source luminance whenthe high frequency noise is 20 microseconds in Embodiment 2.

FIG. 39 illustrates the relation between the exposure time t_(E) and therecognition success rate in Embodiment 2.

FIG. 40 illustrates an example of each mode of a receiver in Embodiment2.

FIG. 41 illustrates an example of an observation method of luminance ofa light emitting unit in Embodiment 2.

FIG. 42 illustrates a service provision system in Embodiment 3.

FIG. 43 is a flowchart of service provision in Embodiment 3.

FIG. 44 is a flowchart of the service provision in another example ofEmbodiment 3.

FIG. 45 is a flowchart of the service provision in another example ofEmbodiment 3.

DESCRIPTION OF EMBODIMENTS

(Underlying Knowledge Forming Basis of the Present Disclosure)

In the visible light communication, the longer the uniquely identifiablevisible light ID transmitted from the visible light transmitter is, thelonger the time for the receiver to complete reception of the visiblelight ID is. The inventors found problems that (1) a user has to waitfor a certain length of time until the reception of the visible light IDis completed and (2) the probability of failure to receive the visiblelight ID is high. Furthermore, the inventors found that this problem issignificant especially in the case where the visible light transmitterthat adopts the frequency-modulation system is used.

Thus, in the technique using the visible light communication, theability to shorten the visible light ID is desired. Furthermore, theability to provide information suitable for a user is desired.

The embodiments below describe a visible light communication system anda visible light communication method in which the visible light ID canbe shortened and a visible light communication system and a visiblelight communication method in which information suitable for a user canbe provided.

A visible light communication method according to an aspect of thepresent disclosure includes: obtaining a first ID identifying an area inwhich a receiver is present; obtaining a second ID by the receiverthrough visible light communication in the identified area; andobtaining, by the receiver, information corresponding to a third IDwhich is a combination of the first ID and the second ID.

Here, in the visible light communication method, the first ID whichidentifies an area in which the receiver is present is used as part ofan ID for obtaining information. By doing so, the second ID obtainedthrough the visible light communication can be shortened, with theresult that the time to complete the visible light communication can becut, and the probability of failure of the visible light communicationcan be reduced.

For example, in the obtaining of a first ID, the first ID may beobtained by referring to a table showing correspondence between thefirst ID and location information obtained by the receiver andindicating a location of the receiver.

For example, the location information may be information indicating thelocation of the receiver identified by a Global Positioning System (GPS)installed on the receiver.

For example, the location information may be information indicating awireless LAN access point accessible by the receiver.

For example, the location information may be information obtained by thereceiver and indicating a store in which the receiver is present.

Furthermore, the visible light communication method according to anaspect of the present disclosure includes: obtaining a first IDindicating an orientation of a receiver; obtaining a second ID by thereceiver through visible light communication; and obtaining, by thereceiver, information corresponding to a third ID which is a combinationof the first ID and the second ID.

Here, in the visible light communication method, the first ID whichindicates an orientation of the receiver is used as part of an ID forobtaining information. By doing so, the second ID obtained through thevisible light communication can be shortened, with the result that thetime to complete the visible light communication can be cut, and theprobability of failure of the visible light communication can bereduced.

For example, it may be that the receiver includes a first camera and asecond camera, and in the obtaining of a second ID, one of the firstcamera and the second camera is selected according to the orientation ofthe receiver and used to obtain the second ID.

Here, an appropriate camera is activated according to an orientation ofthe receiver, with the result that the occurrence of erroneousrecognition of unintended signals and so on can be reduced.

For example, in the obtaining of a first ID, the first ID that indicatesa tilt of the receiver may be obtained.

For example, in the obtaining of a first ID, the first ID may beobtained by referring to a table showing correspondence between the tiltof the receiver and the first ID.

Furthermore, the visible light communication method according to anaspect of the present disclosure includes: obtaining a first IDindicating a user attribute of a receiver; obtaining a second ID by thereceiver through visible light communication; and obtaining, by thereceiver, information corresponding to a third ID which is a combinationof the first ID and the second ID.

Here, in the visible light communication method, the first ID whichindicates an attitude of a user is used as part of an ID for obtaininginformation. By doing so, information suitable for the user can beprovided.

For example, it may be that the visible light communication methodfurther includes obtaining first image data by starting exposuresequentially for a plurality of exposure lines of an image sensor eachat a different time and by capturing a subject with a first exposuretime so that an exposure time of each of the plurality of exposure linespartially overlaps an exposure time of an adjacent one of the pluralityof exposure lines, and the obtaining of a second ID includes: obtainingsecond image data by starting exposure sequentially for the plurality ofexposure lines each at a different time and by capturing the subjectwith a second exposure time shorter than the first exposure time so thatan exposure time of each of the plurality of exposure lines partiallyoverlaps an exposure time of an adjacent one of the plurality ofexposure lines; and demodulating a bright line pattern that correspondsto the plurality of exposure lines and appears in the second image data,to obtain the second ID, and in the obtaining of second image data, thesecond exposure time is set to 1/480 seconds or less to cause the brightline pattern to appear in the second image data.

For example, the visible light communication method may further include:performing processing of receiving a request to distribute informationfrom a requester; distributing, as the information corresponding to thethird ID, the information subject to the request from the requester; andperforming information processing for charging the requester accordingto the distribution of the information.

An identification signal according to an aspect of the presentdisclosure is generated by the visible light communication method andincludes the first ID and the second ID.

By doing so, the second ID obtained through the visible lightcommunication can be shortened, with the result that the time tocomplete the visible light communication can be cut, and the probabilityof failure of the visible light communication can be reduced.

A receiver according to an aspect of the present disclosure is areceiver which receives a signal through visible light communication andincludes: a first ID obtaining unit configured to obtain a first IDidentifying an area in which the receiver is present; a second ID unitconfigured to obtain a second ID through the visible light communicationin the identified area; and an information obtaining unit configured toobtain information corresponding to a third ID which is a combination ofthe first ID and the second ID.

Here, the receiver uses, as part of an ID for obtaining information, thefirst ID which identifies an area in which the receiver is present. Bydoing so, the second ID obtained through the visible light communicationcan be shortened, with the result that the time to complete the visiblelight communication can be cut, and the probability of failure of thevisible light communication can be reduced.

A program according to an aspect of the present disclosure causes acomputer to execute the visible light communication method.

It is to be noted that these general or specific aspects may beimplemented using a system, a method, an integrated circuit, a computerprogram, or a computer-readable recording medium such as CD-ROM, or anycombination of systems, methods, integrated circuits, computer programs,and recording media.

The following describes embodiments in detail with reference to thedrawings as appropriate. Descriptions which are more detailed thannecessary may, however, be omitted. For example, detailed descriptionson already well-known matters and overlapping descriptions onsubstantially the same configurations may be omitted. The reason forthis is to avoid the following description becoming unnecessarilyredundant, thereby helping those skilled in the art easily understandit.

It is to be noted that each of the embodiments described below shows aspecific example of the present disclosure. The numerical values,shapes, materials, structural elements, the arrangement and connectionof the structural elements, steps, the processing order of the stepsetc., shown in the following embodiments are mere examples and do notrestrict the present disclosure. Furthermore, among the structuralelements in the following embodiments, structural elements not recitedin the independent claims each indicating the broadest concept aredescribed as arbitrary structural elements.

Embodiment 1

In this embodiment, an inquiry ID which will eventually be used isdivided as an area ID uniquely set for each area and a visible light IDtransmitted through the visible light communication. By doing so, it ispossible to shorten the visible light ID received by a receiver throughthe visible light communication. Specifically, a mobile terminalidentifies an area in which the mobile terminal is currently present,and obtains an area ID first that corresponds to the identified area. Bydoing so, when a visible light ID is received, visible lighttransmitters from which the visible light ID can be obtained can benarrowed down to a device intended by a user.

Furthermore, other than an explicit user operation to designate an areain which the mobile terminal is currently present, detecting a housingorientation of the mobile terminal allows automatic narrowing down ofvisible light transmitters from which the visible light ID can beobtained. Moreover, the housing orientation of the mobile terminal isused to determine which of a plurality of cameras in the mobile terminalis used, for example. These make it possible to know user's implicitintention.

The following describes this embodiment in detail.

FIG. 1 is a block diagram illustrating a configuration of a visiblelight communication system according to this embodiment. This visiblelight communication system includes: a mobile terminal B0101 which is areceiver; a visible light transmitter B0120; an ID correspondenceinformation conversion server B0111; and an area ID information serverB0141. The mobile terminal B0101 includes an area detection unit B0102,a sensing unit B0103, an inquiry ID generation unit B0104, a visiblelight ID reception unit B0105, a front camera B0106, a back cameraB0107, a communication unit B0108, a display unit B0109, and a userinformation holding unit B0151.

The mobile terminal B0101 receives, using the front camera B0106 or theback camera B0107, visible light emitted by the visible lighttransmitter B0120. The visible light ID reception unit B0105 thenconverts the received visible light into a visible light ID.

Furthermore, the mobile terminal B0101 uses, as information forselecting a visible light ID, information on an area in which the mobileterminal B0101 held by a user is currently present. Specifically, thearea detection unit B0102 detects, using sensing data obtained by thesensing unit B0103, area information related to the area in which themobile terminal B0101 is currently present, to identify the area inwhich the mobile terminal B0101 is currently present.

The inquiry ID generation unit B0104 transmits the detected areainformation to the area ID information server B0141 in order to make aninquiry to the area ID information server B0141 via the communicationunit B0108 for an ID of the area identified by the area detection unitB0102.

The area ID information server B0141 includes a communication unitB0142, an area information determination unit B0143, and an area IDinformation holding unit B0144.

The area ID information server B0141 receives the area informationreceived from the mobile terminal B0101. This area information is passedto the area information determination unit B0143 via the communicationunit B0142.

The area ID information holding unit B0144 holds an area ID informationtable showing correspondence between each area and an area ID foruniquely identifying the area.

The area information determination unit B0143 refers to the area IDinformation table held by the area ID information holding unit B0144, todetermine an area ID that corresponds to the area information receivedfrom the mobile terminal B0101. Subsequently, the area informationdetermination unit B0143 transmits the determined area ID to the mobileterminal B0101 via the communication unit B0142.

The inquiry ID generation unit B0104 generates an inquiry ID bycombining the area ID received from the area ID information server B0141and the visible light ID generated by the visible light ID receptionunit B0105. Subsequently, the inquiry ID generation unit B0104 requeststhe communication unit B0108 to obtain ID correspondence informationthat corresponds to the inquiry ID, with the result that the IDcorrespondence information that corresponds to the inquiry ID isobtained from the ID correspondence information conversion server B0111via a public network B0130.

However, when the inquiry ID which is a combination of the area ID andthe visible light ID does not satisfy a predetermined condition of theinquiry ID, the inquiry ID generation unit B0104 instructs aninterpolation ID generation unit B0110 to generate an interpolation IDfor interpolating the inquiry ID for shortage.

The interpolation ID generation unit B0110 detects, using sensing dataobtained by the sensing unit B0103, an orientation of the mobileterminal B0101, to generate the interpolation ID based on the result ofthe detection. Alternatively, the interpolation ID generation unit B0110generates the interpolation ID based on a user attribute indicated inuser information held by the user information holding unit B0151.Subsequently, an information request which includes the inquiry IDincluding the interpolation ID is transmitted to the ID correspondenceinformation conversion server B0111.

The ID correspondence information conversion server B0111 includes acommunication unit B0112, a conversion information determination unitB0113, and an ID correspondence information holding unit B0114.

The ID correspondence information holding unit B0114 holds a pluralityof pieces of ID correspondence information which correspond torespective inquiry IDs.

When the communication unit B0112 receives the information requestincluding the inquiry ID from the communication unit B0108 of the mobileterminal B0101, the conversion information determination unit B0113obtains, from the ID correspondence information holding unit B0114, theID correspondence information that corresponds to the received inquiryID. Subsequently, the conversion information determination unit B0113passes the obtained ID correspondence information to the communicationunit B0112. The communication unit B0112 transmits the ID correspondenceinformation to the mobile terminal B0101 via the public network B0130.

The following describes the above operation in detail. Firstly, an areadetection process by the mobile terminal B0101 is described. FIG. 2 is aflowchart of the area detection process by the mobile terminal B0101.

Firstly, in Step SB0202, the area detection unit B0102 starts monitoringnotification from the sensing unit B0103 to prepare for calculating anarea in which the mobile terminal B0101 is present.

Next, in Step SB0203, the area detection unit B0102 checks whether ornot notification from the sensing unit B0103 has been received. When nonotification has been received (NO in Step SB0203), the checking isperformed again after a predetermined length of time (SB0203). On theother hand, when notification has been received (YES in SB0203), theprocess proceeds to Step SB0204.

In Step SB0204, the area detection unit B0102 generates, based on thenotification from the sensing unit B0103, area information indicating anarea in which the mobile terminal B0101 is present. The area detectionunit B0102 then passes the generated area information to the inquiry IDgeneration unit B0104.

In Step SB0205, the inquiry ID generation unit B0104 transmits, to thearea ID information server B0141, area information received from thearea detection unit B0102.

FIG. 3 is a flowchart of the process by the area ID information serverB0141 when the area ID information is requested from the mobile terminalB0101.

The process proceeds from Step SB0205 in FIG. 2 to Step SB0301 in FIG.3. In Step SB0301, the communication unit B0142 of the area IDinformation server B0141 checks whether or not the area informationdetected by the mobile terminal B0101 has been received. When the areainformation has not been received (NO in SB0301), the checking isperformed again. When the area information has been received (YES inSB0301), the process proceeds to Step SB0302.

In Step SB0302, the communication unit B0142 passes the received areainformation to the area information determination unit B0143. Next, inStep SB0303, the area information determination unit B0143 makes aninquiry to the area ID information holding unit B0144 for the area IDthat corresponds to the received area information.

In Step SB0304, the area information determination unit B0143 checkswhether or not information that matches the received area information ispresent in the area ID information table held by the area ID informationholding unit B0144.

FIG. 4 illustrates an example of the area ID information table held bythe area ID information server B0141. This area ID information tableincludes an area ID B1901 and area information corresponding to the areaID B1901. The area information includes at least one of GlobalPositioning System (GPS) information B1902, a wireless LAN access pointidentifier B1903, and store information B1904, for example.

As the wireless LAN access point identifier B1903, an identifier SSID ofan access point or an identifier ESSID of a plurality of particularwireless LAN access points in combination is used, for example.Furthermore, the mobile terminal B0101 receives, for example, the storeinformation B1904 from a Wi-Fi (registered trademark) access point or aBluetooth (registered trademark) communication device provided inside astore when a user enters the store.

In Step SB0304, when information matching the area information ispresent (YES in SB0304), the process proceeds to Step SB0305. In StepSB0305, the area ID information holding unit B0144 notifies the areainformation determination unit B0143 of a corresponding area ID. Next,in Step SB0306, the area information determination unit B0143 generatesan area ID notification indicating the area ID and passes the generatedarea ID notification to the communication unit B0142. Next, in StepSB0307, the communication unit B0142 transmits the area ID notificationreceived from the area information determination unit B0143, to themobile terminal B0101 which requested the area ID.

On the other hand, in Step SB0304, when no matching information ispresent (NO in SB0304), the process proceeds to Step SB0308. In StepSB0308, the area ID information holding unit B0144 notifies the areainformation determination unit B0143 that no correspondence informationis present in the area ID information table. Next, in Step SB0309, thearea information determination unit B0143 generates correspondenceinformation unavailable notification indicating that no correspondingarea ID is present, and passes the generated correspondence informationunavailable notification to the communication unit B0142. Next, in StepSB0307, the communication unit B0142 transmits the correspondenceinformation unavailable notification received from the area informationdetermination unit B0143, to the mobile terminal B0101 which requestedthe area ID.

FIG. 5 is a flowchart of a process performed by the mobile terminalB0101 when the mobile terminal B0101 receives the area ID from the areaID information server B0141.

The process proceeds from Step SB0307 in FIG. 3 to Step SB0401 in FIG.5. In Step SB0401, the communication unit B0108 receives the area IDnotification including the area ID from the area ID information serverB0141 and passes the received area ID to the inquiry ID generation unitB0104. Next, in Step SB0402, the inquiry ID generation unit B0104 holdsan area ID indicated in the area ID notification until new areainformation is provided from the area detection unit B0102.

FIG. 6 is a flowchart of the process performed by the mobile terminalB0101 when the mobile terminal B0101 receives the visible light ID fromthe visible light transmitter B0120.

The process proceeds from Step SB0402 in FIG. 5 to Step SB0501 in FIG.6. In Step SB0501, the visible light ID reception unit B0105 waits forinput from a camera that is used to receive the visible light ID, withthe shutter speed of the camera increased.

In Step SB0502, the inquiry ID generation unit B0104 checks whether ornot the visible light ID reception unit B0105 has received the visiblelight ID. When no visible light ID has been received (NO in StepSB0502), the checking is performed again after a predetermined length oftime (SB0502). When the visible light ID has been received (YES inSB0502), the process proceeds to Step SB0503.

In Step SB0502, the inquiry ID generation unit B0104 checks whether ornot the received visible light ID has all the bits (128 bits).Specifically, the inquiry ID generation unit B0104 determines whether ornot the bit number of the received visible light ID is less than orequal to a predetermined bit number (128-bit). When the visible light IDhas all the bits (YES in SB0502), the process proceeds to Step SB0601 inFIG. 7. When the visible light ID does not have all the bits (NO inSB0502), the process proceeds to Step SB0504.

In Step SB0504, the inquiry ID generation unit B0104 checks whether ornot all the bits (128 bits) are obtained by combining the receivedvisible light ID and the area ID received from the area ID informationserver B0141. Specifically, the inquiry ID generation unit B0104determines whether or not the bit number of the received visible lightID and the area ID in total is less than or equal to the predeterminedbit number (128-bit). When all the bits are not obtained (NO in SB0504),the process proceeds to Step SB0801 in FIG. 10. When all the bits areobtained (YES in SB0504), the process proceeds to Step SB0505.

In Step SB0505, the inquiry ID generation unit B0104 generates aninquiry ID which is a combination of the held area ID and visible lightID.

FIG. 7 is a flowchart of the process performed by the mobile terminalB0101 to request the ID correspondence information.

When the result in Step SB0502 in FIG. 6 is NO and after Step SB0505,the process proceeds to Step SB0601. In Step SB0601, in order to obtaininformation related to the inquiry ID (the visible light ID itself orthe ID which is a combination of the visible light ID and the area ID),the inquiry ID generation unit B0104 requests the communication unitB0108 for the information. Next, in Step SB0602, the communication unitB0108 transmits an information request for obtaining ID correspondenceinformation that corresponds to the inquiry ID to the ID correspondenceinformation conversion server B0111 via the public network B0130.

FIG. 8 is a flowchart of the process performed by the ID correspondenceinformation conversion server B0111 when the ID correspondenceinformation is requested by the mobile terminal B0101.

The process proceeds from Step SB0602 in FIG. 7 to Step SB0702 in FIG.8. In Step SB0702, the communication unit B0112 of the ID correspondenceinformation conversion server B0111 checks whether or not theinformation request including the inquiry ID has been received. When noinformation request has been received (NO in Step SB0702), the checkingis performed again after a predetermined length of time (SB0702). Whenthe information request has been received (YES in SB0702), the processproceeds to Step SB0703.

In Step SB0703, the communication unit B0112 notifies the conversioninformation determination unit B0113 of the received inquiry ID. Next,in Step SB0704, the conversion information determination unit B0113makes an inquiry to the ID correspondence information holding unit B0114for the ID correspondence information that corresponds to the receivedinquiry ID. Next, in Step SB0705, the ID correspondence informationholding unit B0114 checks whether or not information that matches thereceived inquiry ID is present in the held correspondence informationtable.

FIG. 9 illustrates an example of the correspondence information tableheld by the ID correspondence information holding unit B0114. Thecorrespondence information table illustrated in FIG. 9 includes aplurality of inquiry IDs B1801 and ID correspondence information B1802that corresponds to each of the inquiry IDs B1801. The inquiry ID B1801corresponds to the inquiry ID generated by the inquiry ID generationunit B0104 of the mobile terminal B0101 and includes, for example, a128-bit string which includes the visible light ID received by themobile terminal B0101 from the visible light transmitter B0120. The IDcorrespondence information B1802 is information for each of the IDs,such as URL, which corresponds to the inquiry ID B1801.

In Step SB0705, when information matching the inquiry ID is present (YESin SB0705), the process proceeds to Step SB0706. In Step SB0706, the IDcorrespondence information holding unit B0114 notifies the conversioninformation determination unit B0113 of the ID correspondenceinformation that corresponds to the inquiry ID in the correspondenceinformation table.

Next, in Step SB0707, the conversion information determination unitB0113 generates ID correspondence information notification including thereceived ID correspondence information and passes the generated IDcorrespondence information notification to the communication unit B0112.Next, in Step SB0708, the communication unit B0112 transmits the IDcorrespondence information notification received from the conversioninformation determination unit B0113, to the mobile terminal B0101 thatrequested the ID correspondence information.

On the other hand, in Step SB0702, when no matching information ispresent (NO in SB0702), the process proceeds to Step SB0709. In StepSB0709, the ID correspondence information holding unit B0114 notifiesthe conversion information determination unit B0113 that nocorrespondence information is present in the correspondence informationtable. Next, in Step SB0710, the conversion information determinationunit B0113 generates correspondence information unavailable notificationindicating that no correspondence information is present in thecorrespondence information table, and passes the generatedcorrespondence information unavailable notification to the communicationunit B0112. Next, in Step SB0708, the communication unit B0112 transmitsthe correspondence information unavailable notification received fromthe conversion information determination unit B0113, to the mobileterminal B0101 that requested the ID correspondence information.

FIG. 10 is a flowchart of the process performed by the mobile terminalB0101 when the mobile terminal B0101 receives a short ID from thevisible light transmitter B0120.

When the result in Step SB0504 in FIG. 6 is NO, the process proceeds toStep SB0801 in FIG. 10. In Step SB0801, the inquiry ID generation unitB0104 makes an inquiry to the visible light ID reception unit B0105about whether the received visible light ID has been obtained by thefront camera B0106 or the back camera B0107. Next, in Step SB0802, thevisible light ID reception unit B0105 responds back to the inquiry IDgeneration unit B0104 whether the visible light ID has been obtained bythe front camera B0106 or the back camera B0107.

Next, in Step SB0803, the inquiry ID generation unit B0104 requests theinterpolation ID generation unit B0110 to generate the interpolation IDwhich is to be added to the visible light ID. Next, in Step SB0804, theinterpolation ID generation unit B0110 generates the interpolation IDusing the sensing data received from the sensing unit B0103 or the userinformation held by the user information holding unit B0151, and passesthe generated interpolation ID to the inquiry ID generation unit B0104.

Next, in Step SB0805, the inquiry ID generation unit B0104 generates aninquiry ID which is a combination of the held area ID, visible light ID,and interpolation ID.

FIG. 11 is a flowchart of the process performed by the mobile terminalB0101 to display information.

The process proceeds from Step SB0708 in FIG. 8 to Step SB0901 in FIG.11. In Step SB0901, the communication unit B0108 of the mobile terminalB0101 receives the ID correspondence information notification includingthe ID correspondence information from the ID correspondence informationconversion server B0111 via the public network B0130. Next, in StepSB0902, the communication unit B0108 of the mobile terminal B0101 passesthe received ID correspondence information to the inquiry ID generationunit B0104.

Next, in Step SB0903, the inquiry ID generation unit B0104 notifies thedisplay unit B0109 that the visible light ID has been received. Next, inStep SB0904, the display unit B0109 displays information related to thecontent of received notification.

FIG. 12 is a flowchart of the process in which the interpolation IDgeneration unit B0110 generates the interpolation ID based on a userattribute. In this flowchart, the user information indicated in FIG. 13and a user attribute correspondence table indicated in FIG. 14 whichshows correspondence between the interpolation ID and the user attributeare used.

FIG. 13 illustrates an example of the user information held by the userinformation holding unit B0151. This user information includes anattribute name B1601, such as name and sex, which represents the userattribute and an attribute value B1602 of a user which corresponds tothe attribute name B1601.

FIG. 14 illustrates an example of the user attribute correspondencetable used by the interpolation ID generation unit B0110 to select theinterpolation ID based on the user attribute. This user attributecorrespondence table includes an interpolation ID B1701 and a userattribute B1702 associated with the interpolation ID B1701.

The interpolation ID generation unit B0110 checks whether or not theuser information indicated in a user attribute table illustrated in FIG.13 matches the condition indicated in the user attribute B1702, andselects the interpolation ID B1701 associated with the condition whichthe user information matches.

For example, the user information illustrated in FIG. 13 indicates thata sex B1603 is male, a membership rank B1604 is premium, and an ageB1605 is 35 years old, with the result that the interpolation ID “1B1”in FIG. 14 is selected.

The following describes the process indicated in FIG. 11. Firstly, inStep SB1002, the interpolation ID generation unit B0110 reads all userattributes held by the user information holding unit B0151. Next, inStep SB1003, the interpolation ID generation unit B0110 retrieves theuser attribute correspondence table held therein which showscorrespondence between the interpolation ID and the user attribute toselect the interpolation ID. It is to be noted that in the case of notholding the user attribute correspondence table, the interpolation IDgeneration unit B0110 may obtain the user attribute correspondence tablefrom an external server via a network.

Next, in Step SB1004, the interpolation ID generation unit B0110determines the interpolation ID that corresponds to the user attributeread from the user information holding unit B0151 and is defined in theuser attribute correspondence table. Next, in Step SB1005, theinterpolation ID generation unit B0110 checks whether or not every userattribute read from the user information holding unit B0151 has beenchecked for its correspondence with the interpolation ID. When thechecking has not been completed (NO in SB1005), the process proceeds toStep SB1004. On the other hand, when every user attribute has beenchecked for its correspondence with the interpolation ID (YES inSB1005), the process proceeds to Step SB1006.

In Step SB1006, the interpolation ID generation unit B0110 determines,for example, the interpolation ID that corresponds to the largest numberof user attributes to be the interpolation ID suitable for the user whois using the mobile terminal B0101, and passes the interpolation ID tothe inquiry ID generation unit B0104.

The following describes the process in which the interpolation IDgeneration unit B0110 identifies an installation location of the visiblelight transmitter B0120 based on the sensing data and reception camerainformation. FIG. 15 is a flowchart of this process. This flowchartassumes identification of a location of the visible light transmitterB0120 under the situation illustrated in FIG. 17.

Firstly, in Step SB1102, from the sensing data detected by anaccelerometer, a gyroscope, and a geomagnetic sensor and received fromthe sensing unit B0103, the interpolation ID generation unit B0110estimates the tilt of the mobile terminal B0101 in X, Y, and Z axisdirections measured at the time when the mobile terminal B0101 receivesthe visible light ID from the visible light transmitter B0120.

Next, in Step SB1103, when receiving the visible light ID from theinquiry ID generation unit B0104, the interpolation ID generation unitB0110 obtains reception camera information indicating whether thevisible light ID has been received by the front camera B0106 or the backcamera B0107 of the mobile terminal B0101.

Next, in Step SB1104, the interpolation ID generation unit B0110 locatesthe visible light transmitter B0120 based on the tilt of the mobileterminal B0101 estimated in Step SB1102 and the reception camerainformation obtained in Step SB1103.

FIG. 16 is a flowchart of the process in which the interpolation IDgeneration unit B0110 generates the interpolation ID based on theinstallation location of the visible light transmitter B0120.

The process proceeds from Step SB1104 in FIG. 15 to Step SB1201 in FIG.16. In Step SB1201, the interpolation ID generation unit B0110 retrievesa location correspondence table held therein which shows correspondencebetween the interpolation ID and the location of the visible lighttransmitter B0120, in order to select the interpolation ID thatcorresponds to the installation location of the visible lighttransmitter B0120. It is to be noted that in the case of not holding thelocation correspondence table, the interpolation ID generation unitB0110 may obtain the location correspondence table from an externalserver or the like via a network.

Next, in Step SB1202, the interpolation ID generation unit B0110obtains, from the location correspondence table, the interpolation IDthat corresponds to the identified installation location of the visiblelight transmitter B0120, and passes the interpolation ID to the inquiryID generation unit B0104.

FIG. 17, FIG. 18A, FIG. 18B, and FIG. 19 illustrate, in detail, thesituations indicated in the flowcharts of FIG. 15 and FIG. 16 in whichthe interpolation ID generation unit B0110 generates the interpolationID based on the installation location of the visible light transmitterB0120.

FIG. 17 illustrates the visible light transmitters B0120 which surrounda user who is using the mobile terminal B0101.

A visible light transmitter B1302 is a visible light transmitter such aslighting on a ceiling; a visible light transmitter B1303 is a visiblelight transmitter such as signage in front of the user; a visible lighttransmitter B1304 is a visible light transmitter such as signage behindthe user; and a visible light transmitter B1305 is a visible lighttransmitter such as lighting on a floor.

The interpolation ID generation unit B0110 identifies whether thereceived visible light ID originates from the visible light transmitterB1302, B1303, B1304, or B1305, using an angle R of the tilt of themobile terminal B0101 and the reception camera information indicatingwhether the camera that received the visible light ID is the frontcamera B0106 or the back camera B0107.

Furthermore, the mobile terminal B0101 selects, using a housingorientation detected using the sensing unit B0103, a camera thatreceives the visible light ID. FIG. 18A and FIG. 18B illustrate examplesof this operation.

The mobile terminal B0101 detects the housing orientation from thesensing data generated by the sensing unit B0103, selects one of thefront camera B0106 and the back camera B0107 based on the housingorientation, and receives visible light B1401 with the selected cameraonly. By doing so, inducement of a wrong operation due to reflectedlight or the like cause can be reduced. In addition, power consumptioncan be reduced.

For example, as illustrated in FIG. 18A, the mobile terminal B0101activates only the front camera B0106 when the tilt of the mobileterminal B0101 is 45 degrees or more. As illustrated in FIG. 18B, themobile terminal B0101 activates only the back camera B0107 when the tiltof the mobile terminal B0101 is less than 45 degrees. It is to be notedthat the angle indicated herein is an angle formed by a tilt with thefront surface (the display screen) facing upward where the directionthat is vertically upward is assumed to be the reference as illustratedin FIG. 18A and FIG. 18B.

FIG. 19 illustrates an example of the location correspondence table usedby the interpolation ID generation unit B0110 to select theinterpolation ID based on a device location.

The location correspondence table illustrated in FIG. 19 includes: aninterpolation ID B1504; reception camera information B1501 indicating acamera used to receive the visible light ID; angle information B1502indicating an angle R of the tilt of the mobile terminal B0101; andlocation information B1503 indicating a location of the visible lighttransmitter B0120 estimated based on the reception camera informationB1501 and the angle information B1502. Furthermore, when the samevisible light transmitter B0120 is designated in the locationinformation B1503, the same interpolation ID B1504 is assigned.

As an example, information in the first row in FIG. 19 is described.When the front camera B0106 is used to receive the visible light ID andthe angle of the mobile terminal B0101 is in the range of 315 degrees to360 degrees or from zero degree to 45 degrees, the mobile terminal B0101determines that the visible light transmitter that transmitted thevisible light ID is the visible light transmitter behind the user who isusing the mobile terminal B0101 (the visible light transmitter B1304 inFIG. 17). Furthermore, the mobile terminal B0101 identifies theinterpolation ID in this case as “1C1.”

The following describes a specific use case of this embodiment. FIG. 20illustrates a usage case of this embodiment.

In FIG. 20, a user visits a store in (1) and takes out the mobileterminal B0101 on a specific sales floor in the store (2), andinformation received from the ID correspondence information conversionserver B0111 is displayed on a screen of the mobile terminal B0101.

FIG. 21 illustrates a configuration example of the inquiry ID which themobile terminal B0101 transmits to the ID correspondence informationconversion server B0111.

The inquiry ID is an identification number for accessing particularinformation via the WEB. Although this embodiment describes the lengthof the bit string of the whole inquiry ID as 128 bits, the inquiry IDmay have any bit length.

The inquiry ID includes a 120-bit area ID B2101 provided from the areaID information server B0141, and an 8-bit particular ID B2102. Theparticular ID B2102 includes at least one of the visible light IDreceived from the visible light transmitter B0120 and the interpolationID generated from the user information held by the mobile terminalB0101. The area ID B2101 is a bit string used to identify a store, anarea, or the like. The particular ID B2102 is a bit string used toidentify a given location inside the store or area.

It is to be noted that the internal configuration of the inquiry ID maybe other than the above configuration. For example, the bit numbers ofthe area ID B2101 and the particular ID B2102 are not limited to theabove bit numbers. For example, the inquiry ID may include a 110-bitarea ID and a 18-bit particular ID.

Furthermore, the sequence of the area ID B2101 and the particular IDB2102 may be any sequence; the particular ID B2102 may be placed beforethe area ID B2101. Furthermore, it may be that no area ID B2101 but onlythe 128-bit particular ID 2102 is included in the inquiry ID. Forexample, the inquiry ID may include the visible light ID and theinterpolation ID only. Here, the interpolation ID includes at least oneof the ID that corresponds to the orientation, etc., of the mobileterminal B0101 and the ID that corresponds to the user attribute.

FIG. 22 illustrates an example in which the mobile terminal B0101generates the inquiry ID.

In Example 1, the mobile terminal B0101 receives the whole 128-bitinquiry ID from the visible light transmitter B0120 not via the area IDinformation server B0141.

In Example 2, the mobile terminal B0101 receives the 120-bit area IDB2101 from the area ID information server B0141 and receives remaining8-bit data from the visible light transmitter B0120.

In Example 3, the mobile terminal B0101 receives the 120-bit area IDfrom the area ID information server B0141, receives a 4-bit visiblelight ID from the visible light transmitter B0120, and generatesremaining 4-bit data from the user attribute, etc., held by the mobileterminal B0101.

FIG. 23 illustrates a detailed use case of Example 2 in FIG. 22.

FIG. 23 illustrates, in (1), a process in the mobile terminal B0101which is performed when a user visits a store. The mobile terminal B0101identifies a store using the GPS or communication of Wi-Fi, Bluetooth,sound, or the like, and requests the area ID information server B0141for the 120-bit area ID that corresponds to the identified store.

FIG. 23 illustrates, in (2), a process in the mobile terminal B0101which is performed when the user takes out the mobile terminal B0101 ona specific sales floor in the store. The mobile terminal B0101 receivesan 8-bit visible light ID from the visible light transmitter B0120, thengenerates a 128-bit inquiry ID which is a combination of the 120-bitarea ID received in (1) and the received 8-bit visible light ID, andrequests the ID correspondence information conversion server B0111 forthe information that corresponds to the inquiry ID.

In (3) of FIG. 23, the ID correspondence information conversion serverB0111 distinguishes the information that corresponds to the 128-bitinquiry ID received from the mobile terminal B0101, and notifies themobile terminal B0101 of the distinguished information. The mobileterminal B0101 displays, on its screen, the information received fromthe ID correspondence information conversion server B0111.

FIG. 24 illustrates a detailed use case of Example 3 in FIG. 22.

FIG. 24 illustrates, in (1), a process in the mobile terminal B0101which is performed when a user visits a store. The mobile terminal B0101identifies a store using the GPS or communication of Wi-Fi, Bluetooth,sound, or the like, and requests the area ID information server for the120-bit area ID that corresponds to the identified store.

FIG. 24 illustrates, in (2), a process in the mobile terminal B0101which is performed when the user takes out the mobile terminal B0101 ona specific sales floor in the store. The mobile terminal B0101 receivesa 4-bit visible light ID from the visible light transmitter B0120.Furthermore, the mobile terminal B0101 identifies a location of thevisible light transmitter B0120 from an orientation, etc., of the mobileterminal B0101, and generates a 4-bit interpolation ID indicating theidentified device location.

Next, the mobile terminal B0101 generates a 128-bit inquiry ID which isa combination of the 120-bit area ID received in (1), the 4-bit visiblelight ID received in (2), and the 4-bit interpolation ID, and requeststhe ID correspondence information conversion server B0111 for theinformation that corresponds to the inquiry ID.

In (3) of FIG. 24, the ID correspondence information conversion serverB0111 distinguishes the information that corresponds to the 128-bitinquiry ID received from the mobile terminal B0101, and notifies themobile terminal B0101 of the distinguished information. The mobileterminal B0101 displays, on its screen, the information received fromthe ID correspondence information conversion server B0111.

It is to be noted that although the mobile terminal B0101 identifies,from the sensing data, an area in which the mobile terminal B0101 iscurrently present, and makes an inquiry to the area ID informationserver B0141 for the area ID that corresponds to the identified area inthe above description, the mobile terminal B0101 may receive the area IDitself as the above store information, for example, from a Wi-Fi accesspoint or a Bluetooth communication device.

As above, the visible light communication system according to thisembodiment has the following features indicated in FIG. 25 to FIG. 27.As indicated in FIG. 25, a first ID obtaining unit (the area detectionunit B0102 and the inquiry ID generation unit B0104) obtains an area ID(a first ID) identifying an area in which the receiver (the mobileterminal B0101) is present (SB3001). It is to be noted that the first IDobtaining unit may obtain the area ID from an external server (the areaID information server B0141) and may directly obtain the area ID from aBluetooth communication device or the like installed in the store, etc.For example, the first ID obtaining unit obtains the area ID byreferring to the area ID information table illustrated in FIG. 4, forexample, which shows the correspondence between the area ID and thelocation information obtained by the receiver and indicating a locationof the receiver. Furthermore, this location information is, for example,(1) information indicating a location of the receiver identified by theGPS installed on the receiver, (2) information indicating a wireless LANaccess point accessible by the receiver, or (3) information obtained bythe receiver and indicating the store in which the receiver is present.

Next, a second ID obtaining unit (the visible light ID reception unitB0105) obtains the visible light ID (a second ID) through the visiblelight communication in the area identified in Step SB3001 (SB3002).

At the end, an information obtaining unit (the inquiry ID generationunit B0104) obtains information corresponding to the inquiry ID (a thirdID) which is a combination of the area ID (the first ID) and the visiblelight ID (the second ID) (SB3003). For example, the informationobtaining unit generates the inquiry ID (the third ID) which is acombination of the area ID (the first ID) and the visible light ID (thesecond ID), and obtains information corresponding to the inquiry ID froman external server (the ID correspondence information conversion serverB0111).

Furthermore, as indicated in FIG. 26, the first ID obtaining unit (theinterpolation ID generation unit B0110) obtains the interpolation ID(the first ID) indicating an orientation of the receiver (the mobileterminal B0101) (SB3101). For example, the first ID obtaining unitobtains the interpolation ID indicating an orientation (tilt) of thereceiver using information obtained by the sensor. Specifically, thefirst ID obtaining unit obtains the interpolation ID by referring to thelocation correspondence table illustrated in FIG. 19, for example, whichshows the correspondence between the tilt of the receiver and theinterpolation ID.

Next, the second ID obtaining unit (the visible light ID reception unitB0105) obtains the visible light ID (the second ID) through the visiblelight communication (SB3102).

At the end, the information obtaining unit (the inquiry ID generationunit B0104) obtains information corresponding to the inquiry ID (thethird ID) which is a combination of the interpolation ID (the first ID)and the visible light ID (the second ID) (SB3003). For example, theinformation obtaining unit generates the inquiry ID (the third ID) whichis a combination of the interpolation ID (the first ID) and the visiblelight ID (the second ID), and obtains information corresponding to theinquiry ID from an external server (the ID correspondence informationconversion server B0111).

Here, the receiver may include the front camera B0106 and the backcamera B0107 (the first camera and the second camera). Furthermore, thesecond ID obtaining unit may select one of the front camera B0106 andthe back camera B0107 according to an orientation of the receiver andobtains the visible light ID using the selected camera.

Furthermore, as indicated in FIG. 27, the first ID obtaining unit (theinterpolation ID generation unit B0110) obtains the interpolation ID(the first ID) indicating a user attribute of the receiver (the mobileterminal B0101) (SB3301). For example, the first ID obtaining unitobtains the interpolation ID by referring to the user attributecorrespondence table illustrated in FIG. 14 which shows thecorrespondence between the user attribute and the interpolation ID.

Next, the second ID obtaining unit (the visible light ID reception unitB0105) obtains the visible light ID (the second ID) through the visiblelight communication (SB3202).

At the end, the information obtaining unit (the inquiry ID generationunit B0104) obtains information corresponding to the inquiry ID (thethird ID) which is a combination of the interpolation ID (the first ID)and the visible light ID (the second ID) (SB3003). For example, theinformation obtaining unit generates the inquiry ID (the third ID) whichis a combination of the interpolation ID (the first ID) and the visiblelight ID (the second ID), and obtains information corresponding to theinquiry ID from an external server (the ID correspondence informationconversion server B0111).

It is to be noted that although these three operations are describedseparately here, these operations may be combined. In other words, theinquiry ID includes the visible light ID and at least one of the areaID, the first interpolation ID indicating the orientation of thereceiver, and the second interpolation ID indicating the user attribute.

Furthermore, the present disclosure may be implemented as the inquiry IDgenerated in the above method.

Moreover, as indicated above in FIG. 25 to FIG. 27, the first IDobtaining unit obtains the first ID in a method other than the visiblelight communication, and the second ID obtaining unit obtains the secondID through the visible light communication in this embodiment. Theinformation obtaining unit then obtains information corresponding to thethird ID which is a combination of the first ID and the second ID. Thus,in this embodiment, the ID obtained in a method other than the visiblelight communication is used in addition to the ID obtained through thevisible light communication so that the data amount of the ID obtainedthrough the visible light communication can be reduced or informationsuitable for a user can be provided.

It is to be noted that the visible light communication is acommunication method in which an imaging element (an image sensor)included in the receiver captures a subject which emits visible lightcorresponding to transmission information, and from an image obtained bythe capturing, the transmission information is obtained. Furthermore,this transmission information indicates (identifies) the subject, forexample. Details of the visible light communication method are describedin Embodiment 2.

Embodiment 2

This embodiment describes an example of the visible light communicationmethod which is used in the visible light communication system in theabove Embodiment 1.

(Observation of Luminance of Light Emitting Unit)

An imaging method is proposed in which, when one image is to becaptured, the exposure starts and ends at different points in time foreach imaging element instead of exposure of all the imaging elements atthe same timing. FIG. 28 illustrates an example where the imagingelements in one line are exposed at the same time, and the exposurestart time is shifted in the order from the closest line in an imagingoperation. Here, the imaging elements exposed at the same time arereferred to as an exposure line, and a line of pixels on an image whichcorresponds to these imaging elements is referred to as a bright line.

When an image is captured with the imaging elements the entire surfacesof which are illuminated with light from a flickering light source, abright line (a line of brightness or darkness of pixel values) appearsalong an exposure line on the captured image as illustrated in FIG. 29.By recognizing this bright line pattern, it is possible to estimate achange in light source luminance at a speed which exceeds the imagingframe rate. This allows communication at a speed higher than or equal tothe imaging frame rate by transmitting a signal as the change in lightsource luminance. In the case where the light source represents thesignal with two kinds of luminance values, the lower one of theluminance values is referred to as LOW (LO), and the higher one of theluminance values is referred to as HIGH (HI). It may be that LOW is astate in which the light source emits no light or in which the lightsource emits light weaker than in HIGH.

By this method, information transmission is performed at the speedhigher than the imaging frame rate.

In the case where the number of exposure lines whose exposure times donot overlap each other is 20 in one captured image and the imaging framerate is 30 fps, it is possible to recognize a luminance change in aperiod of 1.67 millisecond. In the case where the number of exposurelines whose exposure times do not overlap each other is 1000, it ispossible to recognize a luminance change in a period of 1/30000 second(about 33 microseconds). Note that the exposure time is set to less than10 milliseconds, for example.

FIG. 29 illustrates a situation where, after the exposure of oneexposure line ends, the exposure of the next exposure line starts.

In this situation, when transmitting information based on whether or noteach exposure line receives at least a predetermined amount of light,information transmission at a speed of fl bits per second at the maximumcan be realized where f is the number of frames per second (frame rate)and I is the number of exposure lines constituting one image.

Note that faster communication is possible in the case of performingtime-difference exposure not on a line basis but on a pixel basis.

In such a case, when transmitting information based on whether or noteach pixel receives at least a predetermined amount of light, thetransmission speed is film bits per second at the maximum, where m isthe number of pixels per exposure line.

If the exposure state of each exposure line caused by the light emissionof the light emitting unit is recognizable in a plurality of levels asillustrated in FIG. 30, more information can be transmitted bycontrolling the light emission time of the light emitting unit in ashorter unit of time than the exposure time of each exposure line.

In the case where the exposure state is recognizable in Elv levels,information can be transmitted at a speed of flElv bits per second atthe maximum.

Moreover, a fundamental period of transmission can be recognized bycausing the light emitting unit to emit light with a timing slightlydifferent from the timing of exposure of each exposure line.

FIG. 31 illustrates a situation where, before the exposure of oneexposure line ends, the exposure of the next exposure line starts.Specifically, this configuration is that the exposure times of adjacentexposure lines temporally partially overlap each other. With such aconfiguration, (1) the number of samples within a predetermined lengthof time can be set larger as compared to the case where it is not untilthe end of the exposure time of one exposure line that the exposure ofthe next exposure line starts. The increased number of samples withinthe predetermined length of time makes it possible to more appropriatelydetect a light signal generated by a light transmitter that is asubject. This means that the error rate in detection of the light signalcan be reduced. Furthermore, (2) the exposure time of each exposure linecan be set longer as compared to the case where it is not until the endof the exposure time of one exposure line that the exposure of the nextexposure line starts, with the result that even in the case where thesubject is dark, a brighter image can be obtained. In other words, theS/N ratio can be improved. Here, the structure in which the exposuretimes of adjacent exposure lines partially overlap each other does notneed to be applied to all exposure lines, and part of the exposure linesmay not have the structure of partially overlapping in exposure time.With the configuration in which the exposure times of part of theadjacent pairs of the exposure lines do not temporally partially overlapeach other, the generation of an intermediate color due to theoverlapped exposure times on the imaging screen can be reduced so that abright line can be detected more appropriately.

In this situation, the exposure time is calculated from the brightnessof each exposure line, to recognize the light emission state of thelight emitting unit.

Note that, in the case of determining the brightness of each exposureline in a binary fashion of whether or not the luminance is greater thanor equal to a threshold, it is necessary for the light emitting unit tocontinue the state of emitting no light for at least the exposure timeof each line, to enable the no light emission state to be recognized.

FIG. 32 illustrates the influence of the difference in exposure time inthe case where the exposure start time of each exposure line is thesame. In 7500 a, the exposure end time of one exposure line and theexposure start time of the next exposure line are the same. In 7500 b,the exposure time is longer than that in 7500 a. The structure in whichthe exposure times of adjacent exposure lines partially overlap eachother as in 7500 b allows a longer exposure time to be used. That is,more light enters the imaging element, so that a brighter image can beobtained. In addition, since the imaging sensitivity for capturing animage of the same brightness can be reduced, an image with less noisecan be obtained. Communication errors are prevented in this way.

FIG. 33 illustrates the influence of the difference in exposure starttime of each exposure line in the case where the exposure time is thesame. In 7501 a, the exposure end time of one exposure line and theexposure start time of the next exposure line are the same. In 7501 b,the exposure of one exposure line ends after the exposure of the nextexposure line starts. The structure in which the exposure times ofadjacent exposure lines partially overlap each other as in 7501 b allowsmore lines to be exposed per unit time. This increases the resolution,so that more information can be obtained. Since the sample interval(i.e. the difference in exposure start time) is shorter, the luminancechange of the light source can be estimated more accurately,contributing to a lower error rate. Moreover, the luminance change ofthe light source in a shorter time can be recognized. By exposure timeoverlap, light source blinking shorter than the exposure time can berecognized using the difference of the amount of exposure betweenadjacent exposure lines.

As described with reference to FIG. 32 and FIG. 33, in the structure inwhich each exposure line is sequentially exposed so that the exposuretimes of adjacent exposure lines partially overlap each other, thecommunication speed can be dramatically improved by using, for signaltransmission, the bright line pattern generated by setting the exposuretime shorter than in the normal imaging mode. Setting the exposure timein visible light communication to less than or equal to 1/480 secondenables an appropriate bright line pattern to be generated. Here, it isnecessary to set (exposure time)<1/8×f, where f is the frame frequency.Blanking during imaging is half of one frame at the maximum. That is,the blanking time is less than or equal to half of the imaging time. Theactual imaging time is therefore 1/2f at the shortest. Besides, since4-value information needs to be received within the time of 1/2f, it isnecessary to at least set the exposure time to less than 1/(2f×4). Giventhat the normal frame rate is less than or equal to 60 frames persecond, by setting the exposure time to less than or equal to 1/480second, an appropriate bright line pattern is generated in the imagedata and thus fast signal transmission is achieved.

FIG. 34 illustrates the advantage of using a short exposure time in thecase where each exposure line does not overlap in exposure time. In thecase where the exposure time is long, even when the light source changesin luminance in a binary fashion as in 7502 a, an intermediate-colorpart tends to appear in the captured image as in 7502 e, making itdifficult to recognize the luminance change of the light source. Byproviding a predetermined non-exposure vacant time (predetermined waittime) t_(D2) from when the exposure of one exposure line ends to whenthe exposure of the next exposure line starts as in 7502 d, however, theluminance change of the light source can be recognized more easily. Thatis, a more appropriate bright line pattern can be detected as in 7502 f.The provision of the predetermined non-exposure vacant time is possibleby setting a shorter exposure time t_(E) than the time difference t_(D)between the exposure start times of the exposure lines, as in 7502 d. Inthe case where the exposure times of adjacent exposure lines partiallyoverlap each other in the normal imaging mode, the exposure time isshortened from the normal imaging mode so as to provide thepredetermined non-exposure vacant time. In the case where the exposureend time of one exposure line and the exposure start time of the nextexposure line are the same in the normal imaging mode, too, the exposuretime is shortened so as to provide the predetermined non-exposure time.Alternatively, the predetermined non-exposure vacant time (predeterminedwait time) t_(D2) from when the exposure of one exposure line ends towhen the exposure of the next exposure line starts may be provided byincreasing the interval t_(D) between the exposure start times of theexposure lines, as in 7502 g. This structure allows a longer exposuretime to be used, so that a brighter image can be captured. Moreover, areduction in noise contributes to higher error tolerance. Meanwhile,this structure is disadvantageous in that the number of samples is smallas in 7502 h, because fewer exposure lines can be exposed in apredetermined time. Accordingly, it is desirable to use these structuresdepending on circumstances. For example, the estimation error of theluminance change of the light source can be reduced by using the formerstructure in the case where the imaging object is bright and using thelatter structure in the case where the imaging object is dark.

Here, the structure in which the exposure times of adjacent exposurelines partially overlap each other does not need to be applied to allexposure lines, and part of the exposure lines may not have thestructure of partially overlapping in exposure time. Moreover, thestructure in which the predetermined non-exposure vacant time(predetermined wait time) is provided from when the exposure of oneexposure line ends to when the exposure of the next exposure line startsdoes not need to be applied to all exposure lines, and part of theexposure lines may have the structure of partially overlapping inexposure time. This makes it possible to take advantage of each of thestructures. Furthermore, the same reading method or circuit may be usedto read a signal in the normal imaging mode in which imaging isperformed at the normal frame rate (30 fps, 60 fps) and the visiblelight communication mode in which imaging is performed with the exposuretime less than or equal to 1/480 second for visible light communication.The use of the same reading method or circuit to read a signaleliminates the need to employ separate circuits for the normal imagingmode and the visible light communication mode. The circuit size can bereduced in this way.

FIG. 35 illustrates the relation between the minimum change time t_(S)of light source luminance, the exposure time t_(E), the time differencet_(D) between the exposure start times of the exposure lines, and thecaptured image. In the case where t_(E)+t_(D)<t_(S), imaging is alwaysperformed in a state where the light source does not change from thestart to end of the exposure of at least one exposure line. As a result,an image with clear luminance is obtained as in 7503 d, from which theluminance change of the light source is easily recognizable. In the casewhere 2t_(E)>t_(S), a bright line pattern different from the luminancechange of the light source might be obtained, making it difficult torecognize the luminance change of the light source from the capturedimage.

FIG. 36 illustrates the relation between the transition time t_(T) oflight source luminance and the time difference t_(D) between theexposure start times of the exposure lines. When t_(D) is large ascompared with t_(T), fewer exposure lines are in the intermediate color,which facilitates estimation of light source luminance. It is desirablethat t_(D)>t_(T), because the number of exposure lines in theintermediate color is two or less consecutively. Since t_(T) is lessthan or equal to 1 microsecond in the case where the light source is anLED and about 5 microseconds in the case where the light source is anorganic EL device, setting t_(D) to greater than or equal to 5microseconds facilitates estimation of light source luminance.

FIG. 37 illustrates the relation between the high frequency noise t_(HT)of light source luminance and the exposure time t_(E). When t_(E) islarge as compared with t_(HT), the captured image is less influenced byhigh frequency noise, which facilitates estimation of light sourceluminance. When t_(E) is an integral multiple of t_(HT), there is noinfluence of high frequency noise, and estimation of light sourceluminance is easiest. For estimation of light source luminance, it isdesirable that t_(E)>t_(HT). High frequency noise is mainly caused by aswitching power supply circuit. Since t_(HT) is less than or equal to 20microseconds in many switching power supplies for lightings, settingt_(E) to greater than or equal to 20 microseconds facilitates estimationof light source luminance.

FIG. 38 is a graph representing the relation between the exposure timet_(E) and the magnitude of high frequency noise when the high frequencynoise t_(HT) of light source luminance is 20 microseconds. Given thatt_(HT) varies depending on the light source, the graph demonstrates thatit is efficient to set t_(E) to greater than or equal to 15microseconds, greater than or equal to 35 microseconds, greater than orequal to 54 microseconds, or greater than or equal to 74 microseconds,each of which is a value equal to the value when the amount of noise isat the maximum. Though t_(E) is desirably larger in terms of highfrequency noise reduction, there is also the above-mentioned propertythat, when t_(E) is smaller, an intermediate-color part is less likelyto occur and estimation of light source luminance is easier. Therefore,t_(E) may be set to greater than or equal to 15 microseconds when thelight source luminance change period is 15 to 35 microseconds, togreater than or equal to 35 microseconds when the light source luminancechange period is 35 to 54 microseconds, to greater than or equal to 54microseconds when the light source luminance change period is 54 to 74microseconds, and to greater than or equal to 74 microseconds when thelight source luminance change period is greater than or equal to 74microseconds.

FIG. 39 illustrates the relation between the exposure time t_(E) and therecognition success rate. Since the exposure time t_(E) is relative tothe time during which the light source luminance is constant, thehorizontal axis represents the value (relative exposure time) obtainedby dividing the light source luminance change period t_(S) by theexposure time t_(E). It can be understood from the graph that therecognition success rate of approximately 100% can be attained bysetting the relative exposure time to less than or equal to 1.2. Forexample, the exposure time may be set to less than or equal toapproximately 0.83 millisecond in the case where the transmission signalis 1 kHz. Likewise, the recognition success rate greater than or equalto 95% can be attained by setting the relative exposure time to lessthan or equal to 1.25, and the recognition success rate greater than orequal to 80% can be attained by setting the relative exposure time toless than or equal to 1.4. Moreover, since the recognition success ratesharply decreases when the relative exposure time is about 1.5 andbecomes roughly 0% when the relative exposure time is 1.6, it isnecessary to set the relative exposure time not to exceed 1.5. After therecognition rate becomes 0% at 7507 c, it increases again at 7507 d,7507 e, and 7507 f. Accordingly, for example to capture a bright imagewith a longer exposure time, the exposure time may be set so that therelative exposure time is 1.9 to 2.2, 2.4 to 2.6, or 2.8 to 3.0. Such anexposure time may be used, for instance, as an intermediate mode in FIG.40.

Depending on imaging devices, there is a time (blanking) during which noexposure is performed, as illustrated in FIG. 41.

In the case where there is blanking, the luminance of the light emittingunit during the time cannot be observed.

A transmission loss caused by blanking can be prevented by the lightemitting unit repeatedly transmitting the same signal two or more timesor adding error correcting code.

To prevent the same signal from being transmitted during blanking everytime, the light emitting unit transmits the signal in a period that isrelatively prime to the period of image capture or a period that isshorter than the period of image capture.

Embodiment 3

FIG. 42 illustrates a service provision system using the receptionmethod described in any of the foregoing embodiments.

First, a company A ex8000 managing a server ex8002 is requested todistribute information to a mobile terminal, by another company B orindividual ex8001. For example, the distribution of detailedadvertisement information, coupon information, map information, or thelike to the mobile terminal that performs visible light communicationwith a signage is requested. The company A ex8000 managing the servermanages information distributed to the mobile terminal in associationwith arbitrary ID information. A mobile terminal ex8003 obtains IDinformation from a subject ex8004 by visible light communication, andtransmits the obtained ID information to the server ex8002. The serverex8002 transmits the information corresponding to the ID information tothe mobile terminal, and counts the number of times the informationcorresponding to the ID information is transmitted. The company A ex8000managing the server charges the fee corresponding to the count, to therequesting company B or individual ex8001. For example, a larger fee ischarged when the count is larger.

FIG. 43 is a flowchart illustrating service provision flow.

In Step ex8000, the company A managing the server receives the requestfor information distribution from another company B. In Step ex8001, theinformation requested to be distributed is managed in association withthe specific ID information in the server managed by the company A. InStep ex8002, the mobile terminal receives the specific ID informationfrom the subject by visible light communication, and transmits it to theserver managed by the company A. The visible light communication methodhas already been described in detail in the other embodiments, and soits description is omitted here. The server transmits the informationcorresponding to the specific ID information received from the mobileterminal, to the mobile terminal. In Step ex8003, the number of timesthe information is distributed is counted in the server. Lastly, in Stepex8004, the fee corresponding to the information distribution count ischarged to the company B. By such charging according to the count, theappropriate fee corresponding to the advertising effect of theinformation distribution can be charged to the company B.

FIG. 44 is a flowchart illustrating service provision flow in anotherexample. The description of the same steps as those in FIG. 43 isomitted here.

In Step ex8008, whether or not a predetermined time has elapsed from thestart of the information distribution is determined. In the case ofdetermining that the predetermined time has not elapsed, no fee ischarged to the company B in Step ex8011. In the case of determining thatthe predetermined time has elapsed, the number of times the informationis distributed is counted in Step ex8009. In Step ex8010, the feecorresponding to the information distribution count is charged to thecompany B. Since the information distribution is performed free ofcharge within the predetermined time, the company B can receive theaccounting service after checking the advertising effect and the like.

FIG. 45 is a flowchart illustrating service provision flow in anotherexample. The description of the same steps as those in FIG. 44 isomitted here.

In Step ex8014, the number of times the information is distributed iscounted in the server. In the case of determining that the predeterminedtime has not elapsed from the start of the information distribution inStep ex8015, no fee is charged in Step ex8016. In the case ofdetermining that the predetermined time has elapsed, on the other hand,whether or not the number of times the information is distributed isgreater than or equal to a predetermined number is determined in Stepex8017. In the case where the number of times the information isdistributed is less than the predetermined number, the count is reset,and the number of times the information is distributed is counted again.In this case, no fee is charged to the company B regarding thepredetermined time during which the number of times the information isdistributed is less than the predetermined number. In the case where thecount is greater than or equal to the predetermined number in Stepex8017, the count is reset and started again in Step ex8018. In Stepex8019, the fee corresponding to the information distribution count ischarged to the company B. Thus, in the case where the count during thefree distribution time is small, the free distribution time is providedagain. This enables the company B to receive the accounting service atan appropriate time. Moreover, in the case where the count is small, thecompany A can analyze the information and, for example when theinformation is out of season, suggest the change of the information tothe company B. In the case where the free distribution time is providedagain, the time may be shorter than the predetermined time providedfirst. The shorter time than the predetermined time provided firstreduces the burden on the company A. Further, the free distribution timemay be provided again after a fixed time period. For instance, if theinformation is influenced by seasonality, the free distribution time isprovided again after the fixed time period until the new season begins.

Note that the charge fee may be changed according to the amount of data,regardless of the number of times the information is distributed.Distribution of a predetermined amount of data or more may be charged,while distribution is free of charge within the predetermined amount ofdata. The charge fee may be increased with the increase of the amount ofdata. Moreover, when managing the information in association with thespecific ID information, a management fee may be charged. By chargingthe management fee, it is possible to determine the fee upon requestingthe information distribution.

Although the display apparatus, the receiver, and the visible lightcommunication system according to the embodiments in the presentdisclosure have been described above, these embodiments do not restrictthe present disclosure.

Moreover, the respective processing units included in the displayapparatus, the receiver, or the visible light communication systemaccording to the above embodiments are each typically implemented as anLSI which is an integrated circuit. These processing units may beindividually configured as single chips or may be configured so that apart or all of the processing units are included in a single chip.

Furthermore, the method of circuit integration is not limited to LSIs,and implementation through a dedicated circuit or a genera-purposeprocessor is also possible. A Field Programmable Gate Array (FPGA) whichallows programming after LSI manufacturing or a reconfigurable processorwhich allows reconfiguration of the connections and settings of thecircuit cells inside the LSI may also be used.

Furthermore, each of the structural elements in each of theabove-described embodiments may be configured in the form of anexclusive hardware product, or may be realized by executing a softwareprogram suitable for the structural element. Each of the structuralelements may be realized by means of a program executing unit, such as aCPU or a processor, reading and executing the software program recordedin a recording medium such as a hard disk or a semiconductor memory.

Moreover, the present disclosure may be implemented as the aboveprogram, or may be implemented as a non-transitory computer-readablerecording medium on which the above program has been recorded.Furthermore, it goes without saying that the program can be distributedvia a transmission medium such as the Internet.

Moreover, all numerical figures used in the forgoing description areexemplified for describing the present disclosure in specific terms, andthus the present disclosure is not limited to the exemplified numericalfigures. Furthermore, the logic levels represented as HIGH and LOW orswitching states represented as ON and OFF are exemplified fordescribing the present disclosure in specific terms; a differentcombination of the exemplified local levels or switching states can leadto the same or like result.

Furthermore, the separation of the functional blocks in the blockdiagrams is merely an example, and plural functional blocks may beimplemented as a single functional block, a single functional block maybe separated into plural functional blocks, or part of functions of afunctional block may be transferred to another functional block. Inaddition, the functions of functional blocks having similar functionsmay be processed, in parallel or by time-division, by a single hardwareor software product.

Moreover, the sequence in which the steps included in the visible lightcommunication signal display method are executed is given as an exampleto describe the present disclosure in specific terms, and thus othersequences than the above are also possible. Furthermore, part of thesteps may be executed simultaneously (in parallel) with another step.

Although the exemplary embodiments are described above, the Claims inthis application are not limited to these embodiments. Those skilled inthe art would readily appreciate that, without departing from the novelteachings and advantages of the subject matter recited in the appendedClaims, various modifications may be made in the above-describedembodiments and other embodiments may be obtained by arbitrarilycombining structural elements in the above-described embodiments.Therefore, such modification examples and other embodiments are alsoincluded in the present disclosure.

INDUSTRIAL APPLICABILITY

The visible light communication signal display method and the displayapparatus according to the present disclosure enable safe and activeacquisition of information other than images and are, therefore, usablein various applications such as the transfer of image-attachedinformation and information transmission in various scenes in a sensethat such active properties allow necessary information to be safelyobtained as much as needed from signage, information terminals, andinformation display devices outside, let alone devices such astelevisions, personal computers, and tablets in homes.

We claim:
 1. A visible light communication method, comprising: sending auser attribute, by a receiver, to the first server, the user attributebeing pre-stored in the receiver; obtaining a first information, by thereceiver, from the first server, the first information corresponding tothe user attribute; obtaining a second information, by the receiver,through visible light communication with a light source; sending thefirst information and the second information, by the receiver, to thesecond server; and obtaining, by the receiver, information from a secondserver using the first information and the second information.
 2. Avisible light communication apparatus, comprising: a processor; and amemory having thereon a program, the program causes the processor toexecute operations including: sending a user attribute, by a receiver,to the first server, the user attribute being pre-stored in thereceiver; obtaining a first information, by the receiver, from the firstserver, the first information corresponding to the user attribute;obtaining a second information, by the receiver, through visible lightcommunication with a light source; sending the first information and thesecond information, by the receiver, to the second server; andobtaining, by the receiver, information from a second server using thefirst information and the second information.
 3. A non-transitorycomputer-readable recording medium storing an information communicationprogram for performing visible light communication, the visible lightcommunication program causing a computer to execute: sending a userattribute, by a receiver, to the first server, the user attribute beingpre-stored in the receiver; obtaining a first information, by thereceiver, from the first server, the first information corresponding tothe user attribute; obtaining a second information, by the receiver,through visible light communication with a light source; sending thefirst information and the second information, by the receiver, to thesecond server; and obtaining, by the receiver, information from a secondserver using the first information and the second information.
 4. Thevisible light communication method according to claim 1, wherein theuser attribute is membership information related to an institute.
 5. Thevisible light communication method according to claim 4, wherein themembership information is member rank in the institute.
 6. The visiblelight communication method according to claim 1, wherein the firstinformation is obtained by referring to a data table that has aplurality of the first information and a plurality of user attributes,each of the plurality of the first information corresponding to each ofthe plurality of user attributes.
 7. The visible light communicationmethod according to claim 1, wherein the first server and the secondserver are the same.